Feline body language offers information to help you read your cat's health and moods. Cats' tails can form exclamation points of happiness or warn of potential aggression. Although individual cats each possess some unique styles of expression, all felines share certain common tail signals that you can learn to read.
If your cat holds her tail upright as she walks toward you, she is communicating her happiness. A quivering upright tail conveys especially deep pleasure. When your cat is seated in a relaxed posture, a motionless tail curved around her body or a slowly moving tail indicates contentment. Your cat is likely to welcome petting, head scratches and chin scratches at these times. At other times, your cat may walk with her tail held straight out horizontally from her body -- this generally means your cat feels well but may be focused on something other than human attention.
When your cat's tail twitches from side to side, she feels irritated by something. If this happens while you are petting her, it may be a preliminary signal that she wants the contact to end. You may be touching her in a way she does not like or she may have decided petting time is over for the day.
When a cat's tail seems to bristle and expand, the animal feels either scared or angry. Look around to see if another animal has come into her view or if the environment has changed in some other way.
If your cat walks with her tail held downward and slightly away from her body, something is bothering her. Make sure that her environment has not been disturbed in some way. Also, if you have multiple cats, check to see if one of them has behaved aggressively toward the others.
If your cat sits huddled tightly into a ball with her tail around her, check to make sure she is warm enough. When necessary, cats use their tails to protect themselves against cold. A cat walking with a drooping tail may feel sick -- observe more closely for other signs of illness such as lack of interest in food or a tendency to hide.
A cat who carries her tail upright but with a slight hooked shape may feel friendly but uncertain. If you see a cat walking with her tail between her legs, this signals submission either to another animal or to you. If your cat's tail twitches when you are playing with her, this indicates her sense of involvement in the game.